The current literature on infant development points to a continually growing appreciation of the perceptual and learning capabilities of the human newborn. Research has shown the neonate is sensorially precocial and capable of demonstrating perceptual preferences. However, relatively little is known about the sensory and social receptivity of the rapidly increasing population of preterm infants. In our laboratory, using a choice procedure, we have shown that infants as young as one day old can discriminate, and actually prefer to listen to, their own mother's voice versus another female's voice. The general goal of this proposal is to make a substantial contribution to the body of knowledge detailing the behavioral and sensory functions of healthy fullterm newborns and those infants born prior to their expected date of birth. The specific goals are to characterize the response of full- and pre-term infants to the maternal voice and to develop techniques for the assessment of individual differences in this response as a function of gestational age and perinatal experience. Having identified differences in the nature of the neonate's response to the maternal voice, the final goal of this proposal will be to test whether postnatal experience with mother's voice will alter the response of the hospitalized premature infant to vocal stimulation.